Chapter 9
Applying Population Ecology:
The Human Population and
Its Impact
Core Case Study: Is the World
Overpopulated?
 The
world’s population is projected to
increase from 6.6 billion to 8.9 billion
between 2006 and 2050.
 The debate over interactions among
population growth, economic growth, politics,
and moral beliefs is one of the most important
and controversial issues in environmental
science.
Core Case Study: Is the World
Overpopulated?
 Much
of the world’s
population growth
occurs in
developing
countries like China
and India.
Figure 9-1
Core Case Study: Is the World
Overpopulated?
 Some
argue that the planet has too many
people.
 Some feel that the world can support billions
of more people due to technological
advances.
 There is a constant debate over the need to
reduce population growth.

Must consider moral, religious, and personal
freedom.
HUMAN POPULATION GROWTH:
A BRIEF HISTORY
 The
human population has grown rapidly
because of the expansion of agriculture and
industrial production and lower death rates
from improvements in hygiene and medicine.


In 2006, the population of developed countries
grew exponentially at 0.1% per year.
Developing countries grew (15 times faster at
1.5% per year.
Where Are We Headed?
 We
do not know how long we can continue
increasing the earth’s carrying capacity for
humans.



There are likely to be between 7.2-10.6 billion
people on earth by 2050.
97% of growth in developing countries living in
acute poverty.
What is the optimum sustainable population of the
earth based on the cultural carrying capacity?
Where Are We Headed?
 U.N.
world
population projection
based on women
having an average of
2.5 (high), 2.0
(medium), or 1.5
(low) children.
Figure 9-2
High
High
10.6
Medium
Low
Medium
8.9
Low
7.2
Year
Fig. 9-2, p. 173
Demographic Measures
Statistics about people, such
as births, deaths, and where
they live as well as total
population size.
Gross National Product- The most
commonly used measure of the
economic growth of a country. Value of
all goods & services produced.
Per capita = per person
Density- number of people in a
certain space.
Doubling time- The time it takes for the
population to double the number of
people
Rule of 70
Doubling time =
70
Growth Rate
If a population of a country grows at a rate
of 5% a year, the number of years
required for the pop to double is what?
If a population of a country grows at a rate
of 5% a year, the number of years
required for the pop to double is what?
Rule of 70:
Doubling time =
70 = 14 years
5
Immigration- People coming into
the population
Emigration- The movement of
people out of the population.
Net Migration- Total number of
people moving into or out of the
population.
Birth rate (natality)- the number of
births in a year per 1,000 people.
Death Rate (mortality)- the number
of deaths in a year per 1,000
people
Infant mortality rate- Number of
babies out of every 1000 who die
before their 1st birthday.
If a mother lives in an area with a
high infant mortality rate she will
tend to have a lot of children to
ensure some will make it to
adulthood.
FACTORS AFFECTING HUMAN
POPULATION SIZE
 Population
increases because of births and
immigration and decreases through deaths
and emigration.
 Instead
of using raw numbers, crude birth
rates and crude death rates are used (based
on total number of births or deaths per 1,000
people in a population).
Growth Rate- includes birth rate, death rate,
immigration and emigration
Using Raw Numbers:
G.R. = (Births – deaths) + (Immigration – Emigration) X 100
Total Population
If a population of 10,000 experiences 100 births, 40
deaths, 10 immigrants and 30 emigrants in a year, what
is the net annual percentage growth rate?
Growth Rate- includes birth rate, death rate,
immigration and emigration
Using Raw Numbers:
G.R. = (Births – deaths) + (Immigration – Emigration) X 100
Total Population
If a population of 10,000 experiences 100 births, 40
deaths, 10 immigrants and 30 emigrants in a year, what
is the net annual percentage growth rate?
G.R. = (100 – 40) + (10 – 30) X 100 =
10,000
Growth Rate- includes birth rate, death rate,
immigration and emigration
Using Raw Numbers:
G.R. = (Births – deaths) + (Immigration – Emigration) X 100
Total Population
If a population of 10,000 experiences 100 births, 40
deaths, 10 immigrants and 30 emigrants in a year, what
is the net annual percentage growth rate?
G.R. = (100 – 40) + (10 – 30) X 100 = 60 + (-20) X 100
10,000
10,000
Growth Rate- includes birth rate, death rate,
immigration and emigration
Using Raw Numbers:
G.R. = (Births – deaths) + (Immigration – Emigration) X 100
Total Population
If a population of 10,000 experiences 100 births, 40
deaths, 10 immigrants and 30 emigrants in a year, what
is the net annual percentage growth rate?
G.R. = (100 – 40) + (10 – 30) X 100 = 60 + (-20) X 100
10,000
10,000
= 40 = 0.4%
100
Growth rate: Using Crude Rates
 Instead
of using raw numbers, crude birth
rates and crude death rates are used (based
on total number of births or deaths per 1,000
people in a population).
(Birth rate - death rate) + (immigration rate – emigration rate) X 100
1000
Growth rate: Using Crude Rates
 Instead
of using raw numbers, crude birth
rates and crude death rates are used (based
on total number of births or deaths per 1,000
people in a population).
(Birth rate - death rate) + (immigration rate – emigration rate) X 100
1000
G.R. = (Birth rate - death rate) + (immigration rate – emigration rate)
10
Growth rate: Using Crude Rates
If the birth rate is 20, the death rate is 30,
immigration is 40, and the emigration rate is
10, what is the growth rate for this country?
Growth rate: Using Crude Rates
If the birth rate is 20, the death rate is 30,
immigration is 40, and the emigration rate is
10, what is the growth rate for this country?
G.R. = (B.R. – D.R.) + (I.R. – E.R.)
10
Growth rate: Using Crude Rates
If the birth rate is 20, the death rate is 30,
immigration is 40, and the emigration rate is
10, what is the growth rate for this country?
G.R. = (B.R. – D.R.) + (I.R. – E.R.)
10
= (20 – 30) + (40 – 10)
10
Growth rate: Using Crude Rates
If the birth rate is 20, the death rate is 30,
immigration is 40, and the emigration rate is
10, what is the growth rate for this country?
G.R. = (B.R. – D.R.) + (I.R. – E.R.)
10
= (20 – 30) + (40 – 10) = -10 + 30 =
10
10
Growth rate: Using Crude Rates
If the birth rate is 20, the death rate is 30,
immigration is 40, and the emigration rate is
10, what is the growth rate for this country?
G.R. = (B.R. – D.R.) + (I.R. – E.R.)
10
= (20 – 30) + (40 – 10) = -10 + 30 = 20 = 2%
10
10
10
FACTORS AFFECTING HUMAN
POPULATION SIZE
 Average
crude
birth and death
rates for various
groupings of
countries in 2006.
Figure 9-3
Average crude
birth rate
Average crude
death rate
21
World
9
All developed
countries
All developing
countries
Developing
countries
(w/o China)
11
10
23
8
27
9
Fig. 9-3, p. 174
38
Africa
15
Latin and
Central America
21
6
20
Asia
7
Oceania
17
7
United
States
North
America
Europe
14
8
14
8
10
11
Fig. 9-3, p. 174
FACTORS AFFECTING HUMAN
POPULATION SIZE
 The
world’s 10 most
populous countries
in 2006 with
projections in 2025.
Figure 9-4
1.3 billion
1.5 billion
1.1 billion
1.4 billion
China
India
USA
Indonesia
Brazil
Pakistan
Bangladesh
Russia
Nigeria
Japan
300 million
349 million
225 million
264 million
187 million
229 million
166 million
229 million
147 million
190 million
142 million
130 million
135 million
199 million
128 million
121 million
2006
2025
Fig. 9-4, p. 174
Declining Fertility Rates:
Fewer Babies per Women
 The
average number of children that a
woman bears has dropped sharply.
 This
decline is not low enough to stabilize the
world’s population in the near future.
Fertility Rates:
 The
Replacement-level Fertility the number of
children a couple must bear to replace
themselves to stabilize a population is ideally
2.0 children.
 It
is actually slightly higher because some
children die.


2.1 in developed countries
2.5 in developing countries because of higher
infant mortality
Fertility Rates:
 Total
fertility rate (TFR): the average
number of children a woman has during her
reproductive years.
 In
2006, the average global Total Fertility
Rate was 2.7 children per woman.


1.6 in developed countries (down from 2.5 in
1950).
3.0 in developing countries (down from 6.5 in
1950).
When
Total Fertility Rate =
Replacement-level Fertility
Zero population
growth
Case Study: Fertility and Birth Rates
in the United States
 Nearly
2.9 million people were added to the
U.S. in 2006:


59% occurred because of births outnumbering
deaths.
41% came from illegal and legal immigration.
Case Study: Fertility and Birth Rates
in the United States
 In
2006, the total fertility rate in the United
States was slightly > 2.0
Figure 9-5
Births per woman
Baby boom
(1946–64)
Replacement
Level
Year
Fig. 9-5, p. 175
Case Study: Fertility and Birth Rates
in the United States
 The
baby bust that followed the baby boom
was largely due to delayed marriage,
contraception, and abortion.
Figure 9-6
Births per thousand population
Demographic
transition
End of World War II
Depression
Baby boom
Baby bust
Echo baby boom
Year
Fig. 9-6, p. 175
Case Study: U.S. Immigration
 Since
1820, the
U.S. has admitted
almost twice as
many immigrants
and refugees as
all other countries
combined.
Figure 9-8
Number of legal immigrants (thousands)
1907
1914
New laws
restrict
Immigration
Great
Depression
Year
Fig. 9-8, p. 178
Factors Affecting Birth Rates and
Fertility Rates
 The
number of children women have is
affected by:







The cost of raising and educating them.
Availability of pensions.
Urbanization.
Education and employment opportunities.
Infant deaths.
Marriage age.
Availability of contraception and abortion.
Factors Affecting Death Rates
 Death




rates have declined because of:
Increased food supplies, better nutrition.
Advances in medicine.
Improved sanitation and personal hygiene.
Safer water supplies.
 U.S.
infant mortality is higher than it could be
(ranked 46th world-wide) due to:



Inadequate pre- and post-natal care for poor.
Drug addiction.
High teenage birth rate.
POPULATION AGE STRUCTURE
 The
number of people in young, middle, and
older age groups determines how fast
populations grow or decline.
 The number of people younger than age 15 is
the major factor determining a country’s
population growth.
 Changes in the distribution of a country’s age
groups have long-lasting economic and
social impacts.
POPULATION AGE STRUCTURE
 Populations
with a large proportion of its
people in the preproductive ages 1-14 have a
large potential for rapid population growth.
Figure 9-9
Male
Female
Expanding Rapidly
Guatemala
Nigeria
Saudi Arabia
Prereproductive ages 0–14
Male
Female
Expanding Slowly
United States
Australia
Canada
Reproductive ages 15–
44
Male
Female
Stable
Spain
Portugal
Greece
Female
Male
Declining
Germany
Bulgaria
Italy
Postreproductive ages 45–85+
Fig. 9-9, p. 179
Expansive/rapid growth
Birth rate exceeds the
death rate.
Population is getting
larger.
Pyramid shaped
histogram with wide
base.
Stable/Slow Growth (Zero Growth)
Birth rate almost
equals death rate.
The population is not
getting any larger or
is growing very
slowly.
Mainly due
to
immigration
Histogram shape is
straighter and more
box-like until old age
Declining (negative growth)
When the birth rate
is smaller than the
death rate.
The pyramid bulges
near the top or is
inverted.
POPULATION AGE STRUCTURE
 32%
of the people in
developing countries were
under 15 years old in 2006
versus only 17% in
developed countries.
Figure 9-10
Developed Countries
Female
Age
Male
Population (millions)
Fig. 9-10a, p. 179
Developed Countries
Female
Age
Male
Population (millions)
Fig. 9-10b, p. 179
POPULATION AGE STRUCTURE
 Today,
baby boomers make up nearly half of
all adult Americans and dominate the
populations demand for goods and services.
Figure 9-11
Females
1955
Males
Females
1985
Age
Age
Age
Age
Males
Females
2015
Males
Females
Males
2035
Fig. 9-11, p. 180
POPULATION AGE STRUCTURE
Death from AIDS and war can disrupt a
country’s social and economic structure by
removing significant numbers of young adults.
→ leaving very old and very young
POPULATION AGE STRUCTURE
 About
14% of the world’s population live in
countries with stabilizing or declining
populations.
 Global aging may help promote peace.




Fewer young adults available for service
Smaller families → parents more reluctant to
support military that could wipe out offspring
Smaller labor force → competition for workers
between industry & military
Less taxes → decreasing government funds
POPULATION AGE STRUCTURE
A
rapid population
decline can lead to
long-lasting
economic and social
problems.
 The
cost of an aging
population will strain
the global economy.
Figure 9-12
POPULATION AGE STRUCTURE
 Some
problems with
rapid population
decline.
Figure 9-13
• Can threaten economic growth
• Less government revenues with
fewer workers
• Less entrepreneurship and new
business formation
• Less likelihood for new
technology development
• Increasing public deficits to fund
higher pension and healthcare
costs
Fig. 9-13, p. 182
SOLUTIONS: INFLUENCING
POPULATION SIZE
 Demographic
Transition: As countries
become economically developed, their birth
and death rates tend to decline.




Preindustrial stage: little population growth due
to high infant mortality.
Transitional stage: industrialization begins,
death rates drops and birth rates remain high.
Industrial stage: birth rate drops and
approaches death rate.
Postindustrial stage: birth rate drops below
death rate = population is declining
SOLUTIONS: INFLUENCING
POPULATION SIZE
 Generalized

model of demographic transition.
Some developing countries may have difficulty
making the demographic transition.
Figure 9-14
Demographic stages in countriesAs countries becomes
industrialized their birth rates
decline.
Pre-industrial
 Harsh
living conditions lead to a
high birth rate and high death rate.
Thus, little population growth.
Transitional
 As
industrialization begins:
 food production rises
 health care improves.
 So…Death rates drop BUT birth rates
remain high
 The population grows rapidly
 KEY: move countries through this
phase as quickly as possible
Industrial
 Industrialization
is wide spread
 The birth rate drops and eventually
approaches the death rate.
 Population growth slows
Death rate
 This is because of:




Birth rate
better access to birth control
decline in the infant mortality rate
increased job opportunities for women
the high cost of raising children who don’t enter
the work force until after high school or college.
Postindustrial
 The
birth rate declines even further, equaling
the death rate and thus reaching zero
population growth.
 Then, the birth rate falls below the death rate
and the total population size slowly decreases
→ negative growth rate.
 37 countries have reached this stage. (mainly
in W. Europe)
 To most population experts, the challenge is to
help the remaining 88% of the world to get to
this stage.
Stage 1
Preindustrial
Stage 2
Transitional
Stage 3
Industrial
Stage 4
Postindustrial
Birth rate and death rate
(number per 1,00 per year)
High
Birth rate
Death rate
Low
Total population
Increasing
Very high Decreasing
Low
Zero
Negative
Low
Growth rate over time
Fig. 9-14, p. 183
Developing vs. Developed

Developing (Transitional, Third World):
Higher infant mortality rate because of a shortage in prenatal and
pediatric care. Thus, they have more children to ensure some survive.
Agricultural societies need children to help in the labor force.
Lower per capita income or poorer countries need children to provide
an income and sometimes contraceptives are not affordable.
Women lack education and job opportunities.

Developed (Industrial, First World):
Educated and working women tend to delay childbearing.
Pension systems support people as they age.
Family planning and the ability to control fertility.
Higher cost of raising children causes people to have smaller families.
Abortion is legal.
Urbanization





Urbanization is the movement of people from rural
areas into cities
Urban areas must import most of its food, water,
energy, minerals, & other resources because of large
populations
Large populations produce and consume enormous
quantities of resources that can pollute the air, water &
land.
Disease can easily spread in urban areas because of
the high density population.
Environmental pressures of urbanization from population
growth are reduced because birth rates in urban areas
usually are 3-4x’s lower than in rural areas because cities
provide more education and employment opportunities.
SOLUTIONS: INFLUENCING
POPULATION SIZE
 Family
planning has been a major factor in
reducing the number of births and abortions
throughout most of the world.
 Women tend to have fewer children if they
are:




Educated.
Hold a paying job outside the home.
Do not have their human right suppressed.
Have access to contraceptives.
SOLUTIONS: INFLUENCING
POPULATION SIZE
 The
best way to slow population growth is a
combination of:

Elevating the status of women:
• Education
• Jobs
• Human rights


Investing in family planning.
Reducing poverty.
SLOWING POPULATION GROWTH
IN INDIA AND CHINA
 For
more than five decades, India has tried to
control its population growth with only modest
success.
 Since
1970, China has used a governmentenforced program to cut its birth rate in half
and sharply reduce its fertility rate.
Percentage
of world
population
Population
20%
1.1 billion
1.3 billion
1.4 billion
1.6 billion
Population (2050)
(estimated)
Illiteracy (% of adults)
Total fertility rate
Infant mortality rate
47%
17%
36%
Population under age 15 (%)
Population growth rate (%)
20%
1.6%
0.6%
2.9 children per women (down from 5.3 in 1970)
1.6 children per women (down from 5.7 in 1972)
58
27
62 years
70 years
Life expectancy
Percentage living
below $2 per day
GDP PPP per capita
India
China
17%
80
47
$3,120
$5,890
Fig. 9-15, p. 186
India’s Failed
Family Planning Program
 Poor
planning.
 Bureaucratic inefficiency.
 Low status of women.
 Extreme poverty.
 Lack of administrative financial support.
 Disagreement over the best ways to slow
population growth.
China’s Family Planning Program
 Currently,
China’s TFR is 1.6 children per
women.
 China has moved 300 million people out of
poverty.
 Problems:



Strong male preference leads to gender
imbalance.
Average population age is increasing.
Not enough resource to support population.
Some countries, including China, penalize
couples who have more than one or two
children by:
1. Raising their taxes
2. Charging other fees
3. Eliminating income tax deductions for a
couple’s third child
4. Loss of health-care benefits, food allotments
and job options
5. Forced abortions
In China couples who pledge to have no more than
one child receive
1. Extra food
2. Larger pensions
3. Better housing
4. Free medical care
5. Salary bonuses
6. Free school tuition for their one child
7. Preferential treatment in employment when their
child enters the job market.
Because of one-child policies and cultural
issues, in some countries, there is a
strong preference for male children.
1. Girls are aborted at a higher rate than boys
2. Some infant girls are killed
3. Male children receive more education & sometimes are
even fed better than female children.
Result: Rapidly growing gender imbalance or “bride
shortage” → resort to kidnapping brides
Environmental
Impact
Our big footprints
HUMAN ASPECTS ON
NATURAL SYSTEMS
 Excluding
Antarctica,
human
activities have
affect about
83% of the
earths land
surface.
Figure 9-16
HUMAN ASPECTS ON
NATURAL SYSTEMS
 We
have used
technology to alter much
of the rest of nature in
ways that threaten the
survival of many other
species and could
reduce the quality of life
for our own species.
Figure 9-17
Natural Capital Degradation
Altering Nature to Meet Our Needs
Reduction of biodiversity
Increasing use of the earth's net
primary productivity
Increasing genetic resistance of pest
species and disease-causing bacteria
Elimination of many natural predators
Deliberate or accidental introduction
of potentially harmful species into
communities
Using some renewable resources
faster than they can be replenished
Interfering with the earth's chemical
cycling and energy flow processes
Relying mostly on polluting fossil
fuels
Fig. 9-17, p. 188
Environmental Impact
Equation
Population X affluence X technology =
Environmental impact
Developed Countries
 High rates of resource use

Result in high levels of pollution and
environmental degradation per person
 These are believed to be the key factors
determining overall environmental impact.
(Cont….)
•It is estimated that a US citizen
consumes 35 X’s as much as the
average citizen of India and 100 X’s as
much as the average person in the
world’s poorest countries.
•Thus, poor parents in a developing
country would need 70-200 kids to have
the same lifetime environmental impact
as 2 typical US kids.
Reasons for World Hunger Issues
 Unequal
distribution of available food
 Loss of arable land
 Increasing population size
 Increasing poverty in developing countries
 Increasing meat consumption:

Eating higher on the food chain consumes
more resources
• Plant/grain based diets can feed greater number
of people (use less land, water, fuel to produce)
Strategies for ensuring adequate
nutrition for a growing population:
 Increase
the number of new food crops from
a diversity of plant species
 Distribute food more equitably
 Increase land are that is dedicated to grain
production rather than meat production
 Assist developing countries in efficient crop
irrigation systems.
Factors that affect birth & fertility
rates





Importance of kids
in labor force
Urbanization
Cost of raising &
educating kids
Availability of private
& public pensions
Religious beliefs,
traditions & cultural
norms

Educational &
employment
opportunities
 Infant mortality rate
 Average age at
marriage
 Availability of reliable
birth control
SOLUTIONS: INFLUENCING
POPULATION SIZE
 The
best way to slow population growth is a
combination of:

Elevating the status of women:
• Education
• Jobs
• Human rights


Investing in family planning → contraceptives
Reducing poverty.
1994 Global Summit on Population &
Development
 Cairo,
Egypt
 Encouraged action to stabilized the
world’s population at 7.8 billion by
2050, instead of the projected 1112.5 billion.
The major goals are to:
 Provide
universal access to family-planning
services.
 Improve the health care of infants, children &
pregnant women
 Encourage development of national population
policies
 Improving the status of women by expanding
education & job opportunities
Major goals continued:
 Increase
access to education for girls
 Increase men’s involvement in childrearing responsibility & family planning
 Take steps to eradicate poverty
 Reduce & eliminate unsustainable
patterns of production & consumption.